Over the recent years, an IP (Internet Protocol) wireless access technology as typified by a wireless LAN (Local Area Network) based on IEEE 802.11 has shown a sharp advancement. The wireless LAN (based on 802.11n etc) gains a momentum, in which a communication band thereof is as close as 100 Mbps. A large-scale system architecture using the wireless LAN spreads in enterprises, public local governments and educational facilities as well as being oriented to consumers because of ensuring a sufficient communication band and having convenience through a wireless access.
In parallel with such a large-scale system architecture, a variety of IP-based services exhibit wide spread. Especially, real-time services such as VoWLAN (Voice over Wireless LAN) designed for voice traffic via the wireless network are on the verge of becoming a mainstream, and, in addition, it is presumed that non-real-time services such as conventional Web browsing and a file transfer will increasingly rapidly become large in their traffic quantity.
It is broadly known that the wireless LAN is pursuant to the IEEE 802.11 Standard. The IEEE 802.11 Standard specifies only the access control method on the physical layer (PHY) and the MAC sublayer (MAC), in which there remains much flexibility in a system design including node allocation etc.
In terms of these properties, a wireless LAN network infrastructure at the present entails coexistence of three architectures such as a simplex AP architecture, a distributed integration architecture and a centralized integration architecture in the history of its development. Particularly, such a case increases that middle-scale through large-scale wireless LAN systems involve adopting the distributed integration architecture or the centralized integration architecture in terms of integrating-monitoring the LAN systems.    [Patent document 1] Japanese Patent Laid-Open Publication No. 2007-36641